Rainwater chilling, sending back into tank, asking for trouble?

[DJ_L3ThAL]

As title suggests, I'm toying with the idea of a rainwater tank for the house as we are re-doing our gutters. Will use for normal household non-potable uses. Guessing a 1000L or 2000L is about the right size for an average home. Our garden is not water hungry although would get watered every few weeks on average.

Added bonus is I could chill my beer and be fermenting at the end of a brew day, great.

My concern is that a lot of threads I have read the consensus seems to be to simply return the hot water from the chiller back into the rainwater tank. While this would be negligible for an 8000L+ size tank, with a 1000L or 2000L I'd be returning in the order of 15-30% for a triple batch sized chill of near 100C hot water (plate chiller).

Mixing that, let's say 90C, water into the tank would raise the tank water temp up to around 40C (for the 1000L tank example).

My concern is wouldn't this raise the water into a danger zone for harvesting growth, algae, bacteria or whatever other stuff would thrive with a bit of warmth. Sure I'm not drinking the stuff but just a thought I may end up with a pretty filthy rainwater tank needing chlorination at some point which I'd like to avoid. Given the rain we're having it would probably be feasible to send the hot water down the stormwater drain, but obviously better if I could return it to the tank, without any risk.

Anyone in the water industry able to comment and hopefully appease my concern?

 

[wide eyed and legless]

Not in the industry but I have used this method myself, if you are concerned I would be putting a drop of chlorine in the water and holding onto it especially as the Australian Bureau of Meteorology has forecast another El Nino to take effect later this year.

 

[coopsomulous]

Hey DJ

That is exactly how I used to chill my beers before I went to No-Chill. I have a 3000L slim line tank and never had an issue. I was always paranoid of tank water dropping into my beer so I made up bends on my immersion chiller so any drips always fell on the outside of the pot. This was one of the reasons I went to nochill.

I used to sell water tanks a few years ago and algae and bacteria were concerns of customers.

If you are worried about algae growth and bacteria, as long as you are using it on your garden, there is no issue. If you are still worried, a dose of Hydrogen Peroxide will kill anything in there and will decompose into water in a few days. We used to sell a specific product where I used to work and I think it was 30% hydrogen peroxide in water.

Please note that the light colored plastic tanks also allow for algae and bacteria to grow in summer as light still penetrates the tank and the water will warm up slowly.

Anyhow, I don't think you will have any issues as long as the tank water doesn't enter your brew.

Cheers

 

[drsmurto]

I do this but have 2 x 8kL tanks. Temperature change will be small and will become negligible as the tanks will re-equilibrate with the average daily temperature.

Why not go larger than 1-2kL? Plumb the water to toilets, use on garden. Run a 2 or 3 stage filter before it goes into the house for use for drinking, showers etc? This will strip anything potentially growing in your water although I'd be surprised as your water temperature will not remain elevated for too long.

Not sure about Victoria but SA has/had rebates for tanks plus extra rebates if they are plumbed into the house. I got $1000 when I bought the 2nd tank and then had them plumbed in to the house. Tank plus pump plus plumbing was $1600.

 

[MitchD]

I use a tank with my plate chiller and just run the water into the garden, Its nowhere near 100c coming out of the plate chiller probably around 30-40c

 

[Dave70]

We've got a 50,000 L tank, not our main source of potable water, that I hook up the coil chiller to.
I figure the leaf debris, dirt and birdshit getting washed into tank via gutters would be doing far more damage than a little tepid water every now and then.
As mentioned, a little hydrogen peroxide will do the trick if you're worried.

 

[goatus]

Slightly off topic - but I am thinking about doing a DIY rainwater tank coming off my brewshed for brewing water purposes (my mains water is rubbish, I plan to dilute it with this rainwater). Was thinking about using a 200L olive oil barrel and stick a hole in the top with a screen to keep mossies / crap out. But this thread has bought up something i didnt think of - with the small volume vessel, will it be able to heat up too much on hot days? Is this a terrible idea? Keep in mind I will be boiling the water for 60 - 90 minutes when I brew with it.

 

[Ducatiboy stu]

Takes A LOT to heat up 2000ltr of water

Have a long return hose and your problem is solved.

 

[sp0rk]

Our distilling brethren usually use 1000L IBCs for their recirculated cooling water purposes, I'd imagine 2000L would be more than enough

 

[QldKev]

Looking at the maths of it,
75L batch
1000L tank

75/1000 = 7.5% of the water tank vol
If we assume the heat in the 75L wort starts at 100c (for easy maths), and ends at 20c (if the tank water is really cold to get that wort there), so 80% of the heat.
100L x 7.5% x 80% = 6c

So the most you would heat the tank by is 6c.
But real world, some of that heat would be loss to the return hose.

 

[Ducatiboy stu]

The initial temp of the water will play a small factor

The colder the water, the less you will need, meaning the less is being recirculated, reducing the temp rise.

 

[MHB]

I got 5.2oC change in a 1000L tank
It is going to depend on the assumptions you make but
75L and a change from 90oC (after whirlpool) to 20oC 70oC change
75*70=1000*Change is 5,250/1000=5.25oC Change
Not enough to be worried about.

I have bent up a couple of copper hooks for brewers, open the window and hang the return in the gutter, by the time it travels all the way back to the tank it will have cooled down heaps, so no problem. Remember that the water in the tank will cool down reasonably fast anyway, I dint think accelerating algal growth in your water tank will be a problem.
Mark

 

[Funk then Funk1]

Slightly off topic - but I am thinking about doing a DIY rainwater tank coming off my brewshed for brewing water purposes (my mains water is rubbish, I plan to dilute it with this rainwater). Was thinking about using a 200L olive oil barrel and stick a hole in the top with a screen to keep mossies / crap out. But this thread has bought up something i didnt think of - with the small volume vessel, will it be able to heat up too much on hot days? Is this a terrible idea? Keep in mind I will be boiling the water for 60 - 90 minutes when I brew with it.

Our distilling brethren usually use 1000L IBCs for their recirculated cooling water purposes, I'd imagine 2000L would be more than enough

I wouldn't bother with a 200L barrel, like sp0rk has mentioned a 1000L IBC would be much better and not use up all that much more space, You should be able to pick up a decent 2nd hand food grade one for $100.

 

[Dave70]

The initial temp of the water will play a small factor

The colder the water, the less you will need, meaning the less is being recirculated, reducing the temp rise.

Especially when you're starting out at 30 deg.. (12.50)

https://www.youtube.com/watch?v=GM2OhkHhLcg

 

[Cervantes]

I collect the first (and hottest) run of cooling water and use it for cleaning my equipment. If you did this it would only be the cooler water that ran back into the tank.

 

[Airgead]

Been doing this for years but my tank is 5000l so the temp rise won't be as great. I suspect, givem the calcs I saw on here earlier that even on a little 1000l tank you would be fine.

BTW- But a bigger tank that you think you will need. We were tossing up between the 5000l and a 2000 at the time and we are really glad we got the 5000. It has only ever run out on us once. If we had gone 2000l we would have run dry a bunch of times.

Cheers
Dave

Edit - oh yeah... and although the chiller water starts coming back into the tank at close to boiling, it will rapidly cool down as the wort cools. It can never be hotter than the wort. Thermodynamics says that you will never put more heat energy back into the tank than the wort contains so worst case, imagine pouring a kettle full of boiling water into the tank. In my case that's 30l at 100c vs 5000l at 20c...

 

[QldKev]

Prob getting off-topic from the original question, but if you were going to plumb a tank back into the house go at least 5000L. We have a 5000L plumbed just for the toilets and washing machine and it gets emptied way too often. Any water used for cooling in my brewery is normally supplied from the mains, buts then gets directed into the tank for reuse.

 

[WarmerBeer]

Agreed, temperature rise will be negligible, especially if you can run it down a gutter or long house, plus collect your first 20 or so litres for cleaning.
But, buy as big a tank as you can, especially if you think you might want to grow veggies at some stage. I run 2x2000 lt tanks, and most Melbourne summers will empty them at least once or twice. Wish I had 10,000 lt so I could keep the grass green, too

 

[DJ_L3ThAL]

Ive got a plate chiller though, which according to my understanding of heat exchangers will mean if i run it at optimal flow rate the wort should be coming out at 20C and the water quite high at close to the hot wort temperature say 80C-90C?
Otherwise id be wasting water.

Although thinking about that if I'm returning the water anyway id be better running water at a higher flow rate and only having it come out at 40-50C which would be less a drama?


Ps. Thanks for all the comments re: tank sizes. Be nice to water the lawn during summer without worrying about my conscience!!!

 

[Ducatiboy stu]

Especially when you're starting out at 30 deg.. (12.50)

Thank **** I started at 11:59 and finished at 12:59

In an early scene it looked like he had powder under one nostril. Not sure if it was coke or icing sugar, but there was a lot wrong going on.